// 现有base64编码的字符串
// var base64Str = ‘emhhbmdzYW46MTIzNDU2’
// 将base64编码的字符串转化为utf-8编码的字符串，并将还原后的字符串打印到控制台上

 var str=process.argv[2];

 var buf1=Buffer.from(str,'base64');
 var str1=buf1.toString("utf-8");
 var str2=str1.split(":");
 var str3="username:"+str2[0]+" password:"+str2[1];
 console.log(str3);